1. Field of the Invention
The present invention relates to a photocurable inkjet ink and an image forming method.
2. Description of Related Art
Inkjet recording methods have been used in various printing fields, since the methods enable simple and inexpensive image formation. One example of the inkjet recording methods is an UV curable inkjet method in which UV curable ink droplets are landed on a recording medium, and then irradiated with UV rays to form an image. The UV curable inkjet method has recently been drawing attention, since an image having high rubfastness and adhesiveness can be formed also on a recording medium without ink absorbency.
As a method for increasing the pinning property of an UV curable inkjet ink, for example, addition of a gelling agent to an ink for temperature-induced sol-gel phase transition has been studied. Specifically, studies have been made to prevent combining of dots by discharging liquid ink droplets at high temperature and cooling the ink droplets for gelation at the same time they are landed on a recording medium.
The UV curable inkjet ink is typically likely to generate an odor, due to components volatilized from a decomposed matter of an initiator or an unreacted monomer. As a method for reducing such an odor, there have been proposed a method of curing an ink under low oxygen partial pressure to suppress polymerization inhibition by oxygen for reducing unreacted components (e.g., Japanese Patent Application Laid-Open No. 2014-159114: Patent Literature 1; hereinafter, referred to as PTL 1); and a method of introducing a polymerizable group into an initiator to suppress the decomposition of the initiator (e.g., Japanese Patent Application Laid-Open No. 2014-70104: Patent Literature 2; hereinafter, referred to as PTL 2).
It is desirable that an UV curable inkjet ink containing a gelling agent enables the gelling agent to be further dissolved therein stably. As a method for stably dissolving the gelling agent, there has been proposed an UV curable inkjet ink containing a specific hydrophobic (meth)acrylate compound and a polyester acrylate oligomer (e.g., Japanese Patent Application Laid-Open No. 2013-119243: Patent Literature 3; hereinafter, referred to as PTL 3).